scholarly journals Cosmic noise absorption signature of particle precipitation during interplanetary coronal mass ejection sheaths and ejecta

2020 ◽  
Vol 38 (2) ◽  
pp. 557-574
Author(s):  
Emilia Kilpua ◽  
Liisa Juusola ◽  
Maxime Grandin ◽  
Antti Kero ◽  
Stepan Dubyagin ◽  
...  
Keyword(s):  
Energetic Electron ◽  
Geomagnetic Latitude ◽  
Low Frequency ◽  
Occurrence Frequency ◽  
Interplanetary Coronal Mass Ejections ◽  
Interplanetary Coronal Mass Ejection ◽  
Noise Absorption ◽  
Cosmic Noise ◽  
Trapped Radiation ◽  
Mass Ejection

Abstract. We study here energetic-electron (E>30 keV) precipitation using cosmic noise absorption (CNA) during the sheath and ejecta structures of 61 interplanetary coronal mass ejections (ICMEs) observed in the near-Earth solar wind between 1997 and 2012. The data come from the Finnish riometer (relative ionospheric opacity meter) chain from stations extending from auroral (IVA, 65.2∘ N geomagnetic latitude; MLAT) to subauroral (JYV, 59.0∘ N MLAT) latitudes. We find that sheaths and ejecta lead frequently to enhanced CNA (>0.5 dB) both at auroral and subauroral latitudes, although the CNA magnitudes stay relatively low (medians around 1 dB). Due to their longer duration, ejecta typically lead to more sustained enhanced CNA periods (on average 6–7 h), but the sheaths and ejecta were found to be equally effective in inducing enhanced CNA when relative-occurrence frequency and CNA magnitude were considered. Only at the lowest-MLAT station, JYV, ejecta were more effective in causing enhanced CNA. Some clear trends of magnetic local time (MLT) and differences between the ejecta and sheaths were found. The occurrence frequency and magnitude of CNA activity was lowest close to midnight, while it peaked for the sheaths in the morning and afternoon/evening sectors and for the ejecta in the morning and noon sectors. These differences may reflect differences in typical MLT distributions of wave modes that precipitate substorm-injected and trapped radiation belt electrons during the sheaths and ejecta. Our study also emphasizes the importance of substorms and magnetospheric ultra-low-frequency (ULF) waves for enhanced CNA.

scholarly journals Cosmic noise absorption signature of particle precipitation during ICME sheaths and ejecta

2019 ◽  
Author(s):  
Emilia Kilpua ◽  
Liisa Juusola ◽  
Maxime Grandin ◽  
Antti Kero ◽  
Stepan Dubyagin ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Geomagnetic Latitude ◽  
Electron Precipitation ◽  
Occurrence Frequency ◽  
Ulf Waves ◽  
Interplanetary Coronal Mass Ejections ◽  
Noise Absorption ◽  
Radiation Belt Electrons ◽  
Cosmic Noise ◽  
Trapped Radiation

Abstract. We study here energetic (E > 30 keV) electron precipitation using cosmic noise absorption (CNA) during the sheath and ejecta structures of 61 interplanetary coronal mass ejections (ICMEs) observed in the near-Earth solar wind between 1997 and 2012. The data comes from the Finnish riometer chain from stations extending from auroral (IVA, 65.2 geomagnetic latitude, MLAT) to subauroral (JYV, 59.0 MLAT) latitudes. We find that sheaths and ejecta lead frequently to enhanced CNA (> 0.5 dB) both at auroral and subauroral latitudes, although the CNA magnitudes stay relatively low (medians around 1 dB). Due to their longer duration, ejecta typically lead to more sustained enhanced CNA periods (on average 6–7 hours), but the sheaths and ejecta were found to be equally effective in inducing enhanced CNA when relative occurrence frequency and CNA magnitude were considered. Only at the lowest MLAT station JYV ejecta were more effective in causing enhanced CNA. Some clear magnetic local time (MLT) trends and differences between the ejecta and sheath were found. The occurrence frequency and magnitude of CNA activity was lowest close to midnight, while it peaked for the sheaths in the morning and afternoon/evening sectors and for the ejecta in the morning and noon sectors. These differences may reflect differences in typical MLT distributions of wave modes that precipitate substorm-injected and trapped radiation belt electrons during the sheath and ejecta. Our study also emphasizes the importance of substorms and magnetospheric ULF waves for enhanced CNA.

scholarly journals Observations of precipitation energies during different types of pulsating aurora

2020 ◽  
Vol 38 (6) ◽  
pp. 1191-1202
Author(s):  
Fasil Tesema ◽  
Noora Partamies ◽  
Hilde Nesse Tyssøy ◽  
Derek McKay
Keyword(s):  
Electron Density ◽  
Electromagnetic Waves ◽  
Energetic Electron ◽  
Noise Absorption ◽  
Receiver Array ◽  
Maximum Electron Density ◽  
Different Types ◽  
Imaging Receiver ◽  
Cosmic Noise ◽  
Uhf Radar

Abstract. Pulsating aurora (PsA) is a diffuse type of aurora with different structures switching on and off with a period of a few seconds. It is often associated with energetic electron precipitation (>10 keV) resulting in the interaction between magnetospheric electrons and electromagnetic waves in the magnetosphere. Recent studies categorize pulsating aurora into three different types – amorphous pulsating aurora (APA), patchy pulsating aurora (PPA), and patchy aurora (PA) – based on the spatial extent of pulsations and structural stability. Differences in precipitation energies of electrons associated with these types of pulsating aurora have been suggested. In this study, we further examine these three types of pulsating aurora using electron density measurements from the European Incoherent Scatter (EISCAT) VHF/UHF radar experiments and Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) cosmic noise absorption (CNA) measurements. Based on ground-based all-sky camera images over the Fennoscandian region, we identified a total of 92 PsA events in the years between 2010 and 2020 with simultaneous EISCAT experiments. Among these events, 39, 35, and 18 were APA, PPA, and PA types with a collective duration of 58, 43, and 21 h, respectively. We found that, below 100 km, electron density enhancements during PPAs and PAs are significantly higher than during APA. However, there are no appreciable electron density differences between PPA and APA above 100 km, while PA showed weaker ionization. The altitude of the maximum electron density also showed considerable differences among the three types, centered around 110, 105, and 105 km for APA, PPA, and PA, respectively. The KAIRA CNA values also showed higher values on average during PPA (0.33 dB) compared to PA (0.23 dB) and especially APA (0.17 dB). In general, this suggests that the precipitating electrons responsible for APA have a lower energy range compared to PPA and PA types. Among the three categories, the magnitude of the maximum electron density shows higher values at lower altitudes and in the late magnetic local time (MLT) sector (after 5 MLT) during PPA than during PA or APA. We also found significant ionization down to 70 km during PPA and PA, which corresponds to ∼200 keV of precipitating electrons.

Spatial coherence of interplanetary coronal mass ejection-driven sheaths at 1 AU

2020 ◽  
Author(s):  
Matti Ala-Lahti ◽  
Julia Ruohotie ◽  
Simon Good ◽  
Emilia Kilpua ◽  
Noé Lugaz
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Spatial Coherence ◽  
Field Measurements ◽  
Interplanetary Coronal Mass Ejections ◽  
Magnetic Structures ◽  
Interplanetary Coronal Mass Ejection ◽  
Field Fluctuations ◽  
Mass Ejection ◽  
The Magnetic Field

<p><span>We report on the longitudinal coherence of sheath regions driven by interplanetary coronal mass ejections (ICMEs). ICME sheaths are significant drivers of geomagnetic activity at the Earth, with a considerable fraction of ICME-driven storms being either entirely or primarily induced by the sheath. Similarly to Lugaz et al. (2018; doi:10.3847/2041-8213/aad9f4</span><span>), we have analyzed two-point magnetic field measurements made by the ACE and <em>Wind </em>spacecraft in 29 ICME sheaths to estimate the coherence scale lengths, defined as the spatial scale at which correlation between measurements falls to zero, of the field magnitude and components. Scale lengths for the sheath are found to be mostly smaller than the corresponding values in the ICME driver, an expected result given that ICME sheaths are characterized by highly fluctuating, variable magnetic fields, in contrast to the often more coherent ejecta. A relatively large scale length for the magnetic field component in the GSE <em>y</em>-direction was found. We discuss how magnetic field line draping around the ejecta and the alignment of pre-existing magnetic structures by the preceding shock may explain the observed results. In addition, we consider the existence of longitudinally extended and possibly geoeffective magnetic field fluctuations within ICME sheaths, the full understanding of which requires further multi-spacecraft analysis.</span></p>

Intensity and time series of extreme solar-terrestrial storm in 1946 March

2020 ◽  
Vol 497 (4) ◽  
pp. 5507-5517 ◽  
Author(s):  
Hisashi Hayakawa ◽  
Yusuke Ebihara ◽  
Alexei A Pevtsov ◽  
Ankush Bhaskar ◽  
Nina Karachik ◽  
...  
Keyword(s):  
Low Frequency ◽  
Equatorial Electrojet ◽  
Auroral Oval ◽  
Interplanetary Coronal Mass Ejection ◽  
Major Flare ◽  
Instrumental Observations ◽  
Solar Eruptions ◽  
Dip Equator ◽  
Component Amplitude ◽  
Mass Ejection

ABSTRACT Major solar eruptions occasionally cause magnetic superstorms on the Earth. Despite their serious consequences, the low frequency of their occurrence provides us with only limited cases through modern instrumental observations, and the intensities of historical storms before the coverage of the Dst index have been only sporadically estimated. Herein, we examine a solar-terrestrial storm that occurred in 1946 March and quantitatively evaluate its parameters. During the ascending phase of Solar Cycle 18, two moderate sunspot groups caused a major flare. The H α flaring area was recorded to be ≥600–1200 millionths of solar hemisphere, suggesting that this was an M- or X-class flare in soft X-ray intensity. Upon this eruption, a rapid interplanetary coronal mass ejection (ICME) with an average speed of ≈1590 km s−1 was launched. Based on measurements in four known mid-latitude and relatively complete magnetograms, the arrival of this extreme ICME caused a magnetic superstorm, which caused an initial phase with the H-component amplitude of ≥80 nT, followed by a main phase whose intensity was reconstructed as ≤−512 nT using most negative Dst* estimates. Meanwhile, the equatorial boundary of the auroral oval extended down to ≤41${^{\circ}_{.}}$8 in invariant latitude and formed a corona aurora in Watheroo, Australia. Interestingly, during this magnetic superstorm, larger magnetic disturbances were recorded at dusk and near the dip equator on the dayside. Its cause may be associated with a strong westward equatorial electrojet and field-aligned current, in addition to the contribution from the storm-time ring current.

scholarly journals Observations of precipitation energies during different types of pulsating aurora

2020 ◽  
Author(s):  
Fasil Tesema ◽  
Noora Partamies ◽  
Hilde Nesse Tyssøy ◽  
Derek McKay
Keyword(s):  
Electron Density ◽  
Electromagnetic Waves ◽  
Energetic Electron ◽  
Noise Absorption ◽  
Receiver Array ◽  
Maximum Electron Density ◽  
Different Types ◽  
Imaging Receiver ◽  
Cosmic Noise ◽  
Uhf Radar

Abstract. Pulsating aurora (PsA) is a diffuse type of aurora with different structures switching on and off with a period of few seconds. It is often associated with energetic electron precipitation (10 keV) resulted in the interaction between magnetospheric electrons and electromagnetic waves in the magnetosphere. Recent studies categorize pulsating aurora into three different types: amorphous pulsating aurora (APA), patchy pulsating aurora (PPA), and patchy aurora (PA) based on the spatial extent of pulsations and structural stability. Differences in precipitation energies of electrons associated with these types of pulsating aurora have been suggested. In this study, we further examine these three types of pulsating aurora using electron density measurements from the European Incoherent Scatter (EISCAT) VHF/UHF radar experiments and Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) cosmic noise absorption (CNA) measurements. Based on ground-based all-sky camera images over the Fennoscandian region, we identified a total of 92 PsA events in the years between 2010 and 2020 with simultaneous EISCAT experiments. Among these events, 39, 35, and 18 were APA, PPA, and PA types with a collective duration of 58 hrs, 43 hrs, and 21 hrs, respectively. We found that below 100 km, electron density enhancements during PPAs and PAs are significantly higher than during APA. However, there are no appreciable electron density differences between PPA and APA above 100 km, while PA showed weaker ionization. The altitude of the maximum electron density also showed considerable differences among the three types, centered around 110 km, 105 km, and 105 km for APA, PPA, and PA, respectively. The KAIRA CNA values also showed higher values on average during PPA (0.33 dB) compared to PA (0.23 dB) and especially APA (0.17 dB). In general, this suggests that the precipitating electrons responsible for APA have a lower energy range compared to PPA and PA types. Among the three categories, the magnitude of the maximum electron density shows higher values during PPA at lower altitudes and in the late MLT sector (after 5 MLT). We also found significant ionization down to 70 km during PPA and PA, which corresponds to ~ 200 keV energies of precipitating pulsating aurora electrons.

scholarly journals Energetic electron precipitation during sawtooth injections

2007 ◽  
Vol 25 (5) ◽  
pp. 1199-1214 ◽  
Author(s):  
A. J. Kavanagh ◽  
G. Lu ◽  
E. F. Donovan ◽  
G. D. Reeves ◽  
F. Honary ◽  
...  
Keyword(s):  
National Laboratory ◽  
Energetic Electron ◽  
Electron Precipitation ◽  
Optical Observations ◽  
Cosmic Radio ◽  
Magnetospheric Substorms ◽  
Los Alamos National Laboratory ◽  
Sustained Activity ◽  
Noise Absorption ◽  
Cosmic Noise

Abstract. We present simultaneous riometer observations of cosmic noise absorption in the nightside and dawn-noon sectors during sawtooth particle injections during 18 April 2002. Energetic electron precipitation (>30 keV) is a feature of magnetospheric substorms and cosmic radio noise absorption acts as a proxy for qualitatively measuring this precipitation. This event provides an opportunity to compare the absorption that accompanies periodic electron injections with the accepted paradigm of substorm-related absorption. We consider whether the absorption is consistent with the premise that these injections are quasi-periodic substorms and study the effects of sustained activity on the level of precipitation. Four consecutive electron injection events have been identified from the LANL (Los Alamos National Laboratory) geosynchronous data; the first two showing that additional activity can occur within the 2–4 h sawtooth periodicity. The first three events have accompanying absorption on the nightside that demonstrate good agreement with the expected pattern of substorm-absorption: discrete spike events with poleward motion at the onset followed by equatorward moving structures and more diffuse absorption, correlated with optical observations. Dayside absorption is linked to gradient-curvature drifting electrons observed at geostationary orbit and it is shown that low fluxes can lead to a lack of absorption as precipitation is suppressed; precipitation begins when the drifting electron flux surpasses some critical level following continuous injections of electrons from the magnetotail. In addition it is shown that the apparent motion of absorption determined from an azimuthal chain of riometers exhibits an acceleration that may be indicative of an energisation of the drifting electron population.

Flux Rope Model of the 2003 October 28–30 Coronal Mass Ejection and Interplanetary Coronal Mass Ejection

2006 ◽  
Vol 642 (1) ◽  
pp. 541-553 ◽  
Author(s):  
J. Krall ◽  
V. B. Yurchyshyn ◽  
S. Slinker ◽  
R. M. Skoug ◽  
J. Chen
Keyword(s):  
Coronal Mass Ejection ◽  
Flux Rope ◽  
Interplanetary Coronal Mass Ejection ◽  
Mass Ejection

Statistics of pulsating auroras on the basis of all-sky TV data from five stations. I. Occurrence frequency

1981 ◽  
Vol 59 (8) ◽  
pp. 1150-1157 ◽  
Author(s):  
T. Oguti ◽  
S. Kokubun ◽  
K. Hayashi ◽  
K. Tsuruda ◽  
S. Machida ◽  
...  
Keyword(s):  
Local Time ◽  
Cold Plasma ◽  
Geomagnetic Latitude ◽  
Auroral Oval ◽  
Magnetic Activity ◽  
Occurrence Frequency ◽  
Frequency Of Occurrence ◽  
Occurrence Probability ◽  
Energetic Electrons ◽  
Plasma Irregularities

The frequency of occurrence of pulsating auroras is statistically examined on the basis of all-sky TV data for 34 nights from five stations, in a range from 61.5 to 74.3° in geomagnetic latitude. The results are that: (1) occurrence probability of a pulsating aurora is 100% after 4 h in geomagnetic local time, (2) pulsating auroras occur in the morning hours along the auroral oval even when magnetic activity is as small as 0o ≤ Kp ≤ 1, (3) pulsating auroras occur even in the evening when Kp increases to greater than 3−, (4) drift of pulsating auroras is westward in the evening while it is eastward in the morning hours, (5) the region of pulsating auroras splits into two zones, 64 to 68° and 61 to 63° in geomagnetic latitude, after 4 h geomagnetic local time for Kp from 2o to 3−, and the splitting also appears to exist for greater Kp as evidenced by observation other than our auroral data. These results are discussed in relation to distributions of cold plasma irregularities and energetic electrons in the magnetosphere.

scholarly journals Photospheric magnetic field of an eroded-by-solar-wind coronal mass ejection

2016 ◽  
Vol 12 (S327) ◽  
pp. 67-70
Author(s):  
J. Palacios ◽  
C. Cid ◽  
E. Saiz ◽  
A. Guerrero
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Coronal Hole ◽  
Interplanetary Medium ◽  
Flux Rope ◽  
Magnetic Characteristics ◽  
Interplanetary Coronal Mass Ejection ◽  
Fast Wind ◽  
Mass Ejection

AbstractWe have investigated the case of a coronal mass ejection that was eroded by the fast wind of a coronal hole in the interplanetary medium. When a solar ejection takes place close to a coronal hole, the flux rope magnetic topology of the coronal mass ejection (CME) may become misshapen at 1 AU as a result of the interaction. Detailed analysis of this event reveals erosion of the interplanetary coronal mass ejection (ICME) magnetic field. In this communication, we study the photospheric magnetic roots of the coronal hole and the coronal mass ejection area with HMI/SDO magnetograms to define their magnetic characteristics.

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